146 THE SAPROLEGNIACE^ OF THE UISTJTED STATES, 



Figs. 46-49. Saprolegnia torulosa. 



Fig. 46. An oogonium with an antheridium, a rare case. X 200. 



Fig. 47. Two cylindrical members of a series, the upper an oogonium, the lower a sporangium. X 200. 

 Fig. 48. Four members of aseries, an oogonium, two sporangia, and the lowest still young. X 200. 

 Fig. 49. Two oogonia in series. X 200. The pits in the oogonial walls of this species are too inconspicuous to be 

 brought out often with this power. 



Plate XVII. 



Figs. 50-53. Saprolegnia dicUna. 



Fig. 50. The mouths of two sporangia appearing as If burst open by a force from within. X300. 



Pig. 51. An oogonium, with numerous antheridia. X 200. 



Fig. 53. A similar oogonium on a very short branch, its pits few and small. X 540. 



Fig. 53. An oogonium of the small form mentioned in the text. X 200. 



Figs. 54, 55. Saprolegnia asterophora. From Cambridge, Mass. 



Fig. 54. A two-spored oogonium with two antheridia ; alter a sketch by Prof. Trelease. X 850. 



Fig. 55. A one-spored oogonium ; from a slide by Prof. Trelease. X 540. 



Figs. 56-59. Saprolegnia Treleaseana. From Wood's Holl, Mass. 



Fig. 56. The only sporangium yet seen, with a zoospore, s ; after a sketch by Prof. Trelease. X 250. 



Fig. 57. An hypha with two oogonia, one terminal, and one intercalary. X 74. 



Fig. 58. A terminal oogonium, without antheridia. X 350. 



Fig. 59. An intercalary oogonium, with antheridia. X 350. 



Figs. 57-59, from a slide by Prof. Trelease. 

 Figs. 60-68. Pythiopsis cymosa. 



Fig. 60. Two clavate sporangia, one young, a, and one empty, b. X 200. 



Fig. 61. Two globular sporangia, one with its escape-papilla formed and with signs of spore- formation. X 200. 

 Fig. 62. Four sporangia arising by cymose branching of an hypha. X 350. 



Fig. 63. Escape of zoospores from a sporangium with several papillse, only one of which has opened ; z, three zoo- 

 spores killed soon after their escape ; s', two encysted zoospores. X 350. 

 Fig. 64. A smooth-walled oogonium with a very short antheridial branch, x 540. 



Fig. 65. An oogonium with two outgrowths of its wall ; the antheridial branch longer than in 64. X 540. 

 Fig. 66. An oogonium with a single large outgrowth and an antheridial branch of diclinous origin. X 540. 

 Fig. 67. An oogonium with two ripe oospores. X 540. 

 Fig. 68. A ripe oospore showing ils excentric structure, with several oil globules. X 940. 



Plate XVIII. 



Figs. 69-73. Achlya Americana. 



Fig. 69. A recently emptied sporangium, with the spore head. X 200. 



Fig. 70. An liypha bearing numerous sexual organs. X 74. 



Fig. 71. Details of oogonial and antheridial branches. X 350. 



Fig. 72. A part of the ruptured wall of an oogonium, after treatment with chloroiodide of zinc, showing pits. X 540. 



Fig. 73. Two ripe oospores, showing their excentric structure. X 540. 



Figs. 74-77. Achlya menasperma. 



Fig. 74. Ilypha bearing sporangia and oogonia. X 74. 



Fig. 75. Tlie end of an hypha, with oogonial and sterile antheridial branches. X 'i'4. 



Fig. 76. An oogonium with rather numerous antheridial filaments. X 200. 



Fig. 77. An oogonium on a longer branch, with a single antheridium. X 200, 



